Sodium intake in our society averages 20-40 times the physiological requirement. The excess intake, usually as NaCl (salt), is due in part to the sensory pleasure associated with the taste of salt in foods. The proposed studies are designed to delineate the role played by high and low levels of dietary salt in shaping of preferences for salty food. This research will provide insight into how taste regulates salt intake and will also provide valuable information for those wishing to reduce sodium intake. Two studies with adult volunteers will investigate taste response following alterations of dietary sodium. In the first study, the temporal course of changes in pleasantness and intensity judgments of salty taste during hospital-controlled diets with moderate or low levels of sodium will be investigated. Previous studies indicated that a biphasic response to dietary sodium reduction may occur with pleasantness of salty foods first increasing and then later decreasing. Perceived intensity followed an opposite course. This hypothesized biphasic response will be tested directly. In the second study, subjects will be placed on controlled high salt diets where supplemental salt is added either to food and therefore tasted, or taken in capsule form. Pilot studies indicated that taste changes follow increases in salt intake, perhaps mimicking events leading to high salt preference. The pilot work will be extended to investigate hypothetical mechanisms. In the third study, the role of oro-sensory and/or internal receptors in short-term control of human salt appetite will be examined. All three studies will evaluate the role of salivary sodium in taste changes. The fourth study will examine the development of salty food preference in infants and the role dietary experience plays in its ontogeny. Finally, studies will be conducted to develop an appropriate animal model of human salt preference. Eventually, the model will be used to investigate the role of dietary exposure to salt on salt taste preference.